Electric arc control for welding



\NOV. 5,

L. J. LARSON ELECTRIC ARC CONTROL FOR WELDING Filed June 15, 1934INVENTOR. Louis J. Larson 'ATTORNEY.

Patented Nov. 5, 1935 ELECTRIC ARC CONTROL FOR WELDING Louis J. Larson,Milwaukee, Wis., assignor to A. 0.

Smith Corporation, Milwaukee, Wis., a corporation' of New YorkApplication June 15, 1934, Serial No. 730,720

9 Claims.

This invention provides an eificientand sensitive welding arccontroldevice and is particularly adaptable to automatic weldrod feedingdevices of the clutch-driven type.

Referring to the appended drawing:

Figure 1 is a schematic drawing of a weldrod feeding device embodying'the invention.

Figs. 2, 3, 4, 5, and 6 are schematic drawings from a clutch I1 havingfixed and reciprocablerotating members [8 and I9, respectively. Re-

ciprocable member I9 is rotated by any suitable driving means such asmotor 20. A continuous constant speed of such rotation is satisfactory.

The rate of'rotation of clutch member I9 is determined by the ratio ofthe speed reduction Hi, the desired rate of consumption of weldrod lland the amount of excess weldrod feeding rate that it is found desirableto have to make the rate of adjustment of the arc sensitive to rapidchanges of said are. It is desirable to employ a speed of member l9considerably in excess of that corresponding to the average rate ofconsumption of weldrod ll.

Clutch member I! is reciprocated into contacting or driving relationwith driven member l8 and into open or non-driving position by means oflever 2| pivoted at point 22. Magnetic solenoid 23 serves to engageclutch I 1 when auxiliary contact 24 closes the electriccircuitconnecting said coil 23 to the source of electricv energy 25-26.

Spring 21 serves to disengage clutch l1 and dis: continue the feed ofweldrod II when coil 21 is de-energized by the opening of contact 24.

With motor 20 rotating at a selected speed, when the arc becomes longand the arc voltage high the engaging of the clutch I'I causes theweldrod H to be quickly fed toward the work and the arc shortened andthe voltage reduced. And when the arc is short, by disengaging clutchI1, all feed of rod II is discontinued, and the arc consumes theweldrod, lengthening the arc and increasing the voltage across the arc.These operations are automatically performed by the closing and openingof contact 24 by means of 66 solenoid 28 which is here shown asconnected di' rectly across the are at points l2 and I 3 and is 0 kresponsive to the voltage of the arc.

When the voltage of the arc becomes great enough, solenoid 28 overcomesspring 28 and closes contacts 24, energizing solenoid 23, engag 5 ingclutch l1, and causes rod H to be fed toward the work l2. Converselywhen the arc voltage becomes low the spring 29 overcomes the pull oisolenoid 28, and the feed of rod l I is discontinued. Resistance 30 isprovided to adjust the current 10 flowing in solenoid coil 28 andthereby obtain the desired voltage at the are for the work to beperformed.

Due to the natural friction and inertia of the parts of the apparatus anappreciable deviation 15 of the arc length and voltage from the desiredvalues for which the apparatus has been adjusted is necessary to causeclutch ll to open or close. Such deviation from the desired optimumconditions is made greater also by the fact that a 20 change from opento closed condition of the clutch changes the rate of feed of theelectrode from zero to the maximum rate, which carries the correctionbeyond-the desired condition.

Additional mechanism has been added to com- 25 pel the apparatus torapidly engage and disengage the rod feeding means when the arccharacteristics approach their .preferred values, thus providing aproper continued average speed of feed at the point of optimum areconditions by 30 the summation of many short time impulses of feedingaction.

The above result is reached in the arrangement disclosed in Fig. 1 bythe following means: An adjustable resistance 3| is connected in shuntto 36 solenoid coil 28 through contacts 32. Resistance 3| is adjusted toby-pass a desired amount of current from coil 28 when contacts 32 close.

With this arrangement when the arc becomes suiiiciently long and the arcvoltage suiiiciently 40 high solenoid 28 closes contacts 24, solenoid 22is energized, the clutch ll closed, and the feed of the weldrod started.Immediately upon the closing of clutch I1, however, contacts 22 areclosed, coil 28 shunted through resistance 3|, and 48 the pull ofsolenoid 28 is weakened by the amount of the shunted current. If thepull of solenoid 28 is still greater than that of spring 29 because ofthe great lengthof the arc, contacts 2| will 7 remain closed and thefeed of the weldrod will continue at the maximum rate to quickly reducethe arc length. Such feed will continue until the weakened pull ofsolenoid 28 permits contacts 28 to open, whereupon the clutch I! will bedisengaged and the feed cease. But since" the optimum are conditionshave not yet been reached and the shunt circuit has now been opened bythe opening of clutch l1, full strength pull is restored to solenoid 28,whereupon it immediately .closes contacts 24 and the feed is resumed,but

immediately thereafter the resulting closing of contacts 32 againweakens the pull of solenoid 28 and its contacts again open. It will beseen that the apparatus is thereafter compelled to rapidly apply aseries of feeding impulses to the weldrod feed, so long as the arecharacteristics remain within that range near the optimum desiredcharacteristics, determined by the setting of the shunting resistance 3l. The feed will then return to a continued steady rapid condition onlywhen some major disturbance of the arc takes place such as theencountering of a cavity in the work which suddenly lengthens the arebeyond the selected range.

Fig. 2 is a diagrammatic drawing of a modified form of apparatusembodying the invention, in which the control of the arc is eifectuatedin response to the current flowing in the arc. Solenoid 28 is connectedin shunt to resistance 33 which is in series with the arc current. Thecurrent in solenoid 28' is in proportion to the arc current. Contacts 24have been arranged in Fig. 2 to open when the pull of solenoid 28becomes suiliciently large, whereas in Fig. 1, where coil 28 was acrossthearc voltage, contacts 24 were arranged to close when the pull ofsolenoid 28 increased to a predetermined value. Contacts 32 havelikewise been changed in Fig. 2, so that they open when the clutchcloses; whereas, in Fig. 1 they closed when the clutch closed.

The operation of the mechanism in Fig. 2 is as follows:

If the clutch IT is open and no feed of the rod H is taking place,contacts 32' are closed and the pull of solenoid 28' is weakened by thecurrent shunted through resistance 3|. If the arc lengthens sufficientlythe current in the arc and also in coil 28' is reduced, and when a givenvalue is reached the pull of solenoid 28' will be reduced to a point atwhich spring 29 will close contacts 24. The clutch will then close,feeding weldrod l l toward the work. But immediately upon the closing ofclutch I'I, contacts 32' are opened, thereby opening the shunt circuitto coil 28'. The pull of solenoid 29' is thereby increased and thencauses contacts 24 to open. The cycle of operation is then repeated asdescribed in connection with Fig. 1 and will continue as long as the arccharacteristics are within the adi'usted range.

Fig. 3 shows an additional manner of obtaining the positive vibratingaction of the control mechanism and a regular continued series ofweldrod feeding impulses for a selected optimum range of arccharacteristics.

The operation of the arrangement shown in Fig. 3 is much the same asthat of Fig. 2. Coil 28 is operated by the current flowing through thearc, being in this case a coil in series with the arc instead of one inshunt to a resistor in series with such are current as was the case inFig. 2. Since no adjustment resistance is now provided to adjust theaction of solenoid 28 for various desired arc lengths, an adjustmentscrew 34 is provided for spring 29 for setting the device to maintain agiven arc length. When the pull of solenoid 28 becomes suificiently weakto permit spring 29 to close contacts 24, coil 23 is energized andclutch I] closed, causing the weldrod to be fedto'ward the work,whereupon contacts 32 are closed and newly provided solenoid 35 placedacross the are through connections in series with resistance 3|. Thisarc shunt coil 35 then adds to the pull on spring 29 and causes contacts24 to open and stop the weldrod feed. In this man- 5 ner the desiredvibrating action of the feeding mechanism is produced.

During the vibrating motion, in all of the mechanisms here described,the ratio of the time during which the feedtakes place to the total timevaries with small variations in the arc characteristics. This ratio atthe condition of optimum are characteristic is approximately the ratioof the average rate of weldrod consumption to the maximum rate at whichmotor 20 feeds the rod when the clutch is engaged. This ratio increasesas the arc lengthens above the optimum or predetermined arc length anddecreases when the length of the arc is below such value.

In Fig. 3 some advantage is gained by the employment of coil 35connected across the arc, since the longer the arc, the stronger thepull in coil 35, and the quicker it operates to reopen contacts 24.Still greater sensitivity can be obtained by'connecting a battery inseries with the connections of coil 35 and opposed to the voltage of thearc. Such an arrangement of the circuit of coil 35 is shown in Fig. 4,in which battery 36 is opposed to the arc voltage in the circuit of coil35.

In Fig. 3 coil can also be connected across any source of constantpotential and function in the combination to produce the desiredvibrating action of the weldrod feeding mechanism.

In all of the figures so far described the source 35 of energy 25-26 tothe solenoid operating the clutch can be the are circuit.

There is some advantage in employing one mechanism directly responsiveto the arc characteristics to control the operation of a further 40mechanism which operates the electrode feeding means as shown in thedevices already described. However, it is possible to obtain the desiredforced impulse feed of the weldrod when the clutch operating solenoid isitself directly responsive to the are characteristics without theintervention of a separate magnetic unit applied to the arc. Figs.

5 and 6 illustrate such arrangements.

In Fig. 5 shunt coil 31 which is employed to operate the clutch drivefor the weldrod feeding device is connected directly across the arethrough adjusting resistance 39 and is arranged to engage the clutch andfeed the electrode toward the are when the arc voltage rises to aselected value and spring 39 operates to open the clutch and discontinuesuch feed when the arc shortens and its voltage lowers to a given value.

In addition a resistance 40 is connected in shunt to solenoid coil :1through contacts 4| which are open when clutch I1 is disengaged and 00closed when said clutch is engaged.

When the arc voltage rises to a sufiiciently high value to causesolenoid 31 to overcome spring 39 clutch I1 is engaged and the electrodefed toward the are, but immediately therein contacts 63 4| close and thepull of coil 31 is weakened by the which is adjusted for a given arclength by nut 44. Magnet 45 which is connected to voltage source 46through resistance 41 and contacts 48 sumed. These cycles of impulsedrives of electrode ll toward the are III is forced to continue as inthe previous illustrations of the invention.

No are striking mechanism is shown in any of the drawings but anysuitable mechanism may be employed. Mechanisms completely satisfactoryfor such use are shown in the Patent, No. 1,930,- 290, to RichardStresau.

Exceptionally senstive and satisfactory control of the welding electrodefeed and the welding arc characteristics is obtained by the practice ofthe above-described invention. Various modifications of disclosuresherein included may be made by one skilled in the art without departingfrom the spirit of the invention described and claimed.

I claim:

1. A welding electrode feeding device comprising means under the controlof a characteristic of the arc to automatically feed said electrode tothe arc and means actuated by the feeding movement initiation to compelsaid feeding mechanism to feed said electrode by a sustained series ofimpulse feedings when the arc characteristics are at or near theiroptimum for which the feeding device is adjusted.

2. A welding electrode feeding device comprising means under the controlof a characteristic of thearc to automatically feed said electrode to dthe arc and means actuated by the engagement of the feeding means tocompel said feeding mechanism to feed said electrode by a sustainedseries of regular intermittent feeding impulses in which the ratio ofthe feeding time to the total time increases as the average arc voltagerises, and decreases as the average arc voltage decreases.

3. An automatic arc welding electrode feeding device comprisingclutch-driven means to feed said electrode toward the welding arc,magnetic means'controlled by a characteristic of said are to engage anddisengage said clutch, and means actuated by the engagement of thefeeding means to compel said magnetic means to actuate said drivingclutch in a series of driving impulses for all values of the arccharacteristics within a selected range at and near the desired arccondition.

4. An automatic arc welding electrode feeding device comprising amagnetic relay, the actuating coil of which is connected in shunt to thearc, a magnet operated clutch feeding mechanism actuated by said relayfor feeding the electrode to the work, and means responsive to saidclutch mechanism to modify the action of the are upon said relay andforce the feeding mechanism to operate in intermittent impulses within aselected range of arc characteristics.

5. An automatic feeding mechanism for an arc welding electrodecomprising an interruptable feeding device, a relay arranged to open andclose under the influence of the current characteristic of the weldingarc and effect the operation of said 6 feeding device, and meansresponsive to said feeding device to modify the action of the arccurrent upon said relay to regularly interrupt the feeding of saidelectrode.

6. An automatic feeding mechanism for an are 10 welding electrodecomprising an-interruptable feeding device, means under the control of acharacteristic of the arc current to engage and disengage said feedingdevice and thereby effect the feeding of said electrode and meansresponsive 15 to the movements of said feeding device to modify theaction of said are current characteristic upon said first named means toregularly interrupt the feeding of said electrode when the arc currentcharacteristics are near the optimum values for 20 which the device isadjusted to thereby increase the sensitivity of control of the rod feed.

7. An automatic feeding mechanism for an arc welding electrodecomprising a continuously operative feeding device, means under controlof a 26,

characteristic of the welding current to engage and disengage saidfeeding device, and electric current conducting means superimposing uponsaid welding current characteristic modifications thereof to cause theengagement and disengage- 30 ment of said feeding device to assume arapid periodicity at and near the optimum condition of said arc currentcharacteristic for which the apparatus is adjusted.

8. An automatic feeding mechanism for an are 36 welding electrodecomprising a continuously operative feeding device, means under controlof a characteristic of the welding current to engage and disengage saidfeeding device, and electric current conducting means superimposing upon40,

said welding currnt characteristic modifications thereof to cause theengagement and disengagement of said feeding device to assume a rapidperiodicity at and near the optimum condition of said are currentcharacteristic for which the apparatus is adjusted, and to permit thefeeding device to feed continuously when the lengthening of the arechanges said arc current characteristic a predetermined amount from saidoptimum.

9. An automatic feeding mechanism for an arc welding electrodecomprising a continuously operative feeding device, means under controlof a characteristic of the welding current to engage and disengage saidfeeding device, and electric current conducting means superimposing upon65.

said welding current characteristic modifications thereof to cause theengagement and disengagement of said feeding device to assume a rapidperiodicity at and near the optimum condition of said are currentcharacteristic for which the apparatus is adjusted and cause the ratioof the time of feed to the total time of said period to increase as thesaid are current characteristic is changed within said optimum range bythe raising of the voltage across said arc.

LOUIS J. LARSON.

